"It's not just what they do, it's who they are," Biden said. "It's who Sean Collier was. It's also what officer Dennis Simmonds, who put his life on the line last year in a shootout to hunt down the killers and he suffered a severe injury and ultimately he has succumbed."

Biden recognized Collier, who was killed during the manhunt for the marathon bombing suspects, and another, Simmonds, who died last Thursday.

Simmonds, 28, was a rising star in the Boston Police Department. According to Chief Willie Gross, he was recognized for his dedication to fighting youth violence and for his bravery in the Watertown shootout with the marathon bombing suspects one year ago.

"He was really truly the model of what we want our future officers to be," Gross said.

According to a report obtained by WCVB, Simmonds injured his hand, back and ankle and suffered blurriness in his vision in Watertown and was relieved of his duties for a month.

"He was thrown from his feet, knocked to the ground and they kept fighting to protect each other," Gross said. "It's unfortunate. We definitely believe that could have contributed and may have contributed to this untimely death."

When he was asked if he would like to see more charges brought against the bombing suspect, Gross said, "Absolutely. If this contributed in any way, absolutely. What they did was a cowardly act. There's no other way to describe it."

Simmonds' father said he doesn't know if there was a connection between his son's death and the events that took place in Watertown.